export const LOCALES = ["tr", "en", "de"] as const;

export type Locale = (typeof LOCALES)[number];

export const DEFAULT_LOCALE: Locale = "tr";

export const LOCALE_COOKIE = "locale";

export const LOCALE_LABELS: Record<Locale, string> = {
    tr: "TR",
    en: "EN",
    de: "DE",
};

export function isLocale(value: string): value is Locale {
    return (LOCALES as readonly string[]).includes(value);
}

export function matchLocale(acceptLanguage: string | null): Locale {
    if (!acceptLanguage) {
        return DEFAULT_LOCALE;
    }
    const preferences = acceptLanguage
        .split(",")
        .map((part) => {
            const [range, ...params] = part.trim().split(";");
            let q = 1;
            for (const param of params) {
                const match = param.trim().match(/^q=([0-9.]+)$/);
                if (match) {
                    q = Number(match[1]);
                }
            }
            return { range: range.toLowerCase(), q };
        })
        .sort((a, b) => b.q - a.q);

    for (const { range } of preferences) {
        if (range === "*") {
            return DEFAULT_LOCALE;
        }
        const base = range.split("-")[0];
        if (isLocale(base)) {
            return base;
        }
    }
    return DEFAULT_LOCALE;
}